Scale formation or deposition can produce numerous problems across a wide range of applications. Exemplary problems involving scale formation include but are not limited to reduced heat transfer efficiency, flow restrictions and plugging, underdeposit corrosion, microbiological growth, cleaning costs, equipment damage and failure. Generally, scale formation adversely impacts many companies by contributing to lost production, increasing operating costs, and increasing capital equipment costs.
Many minerals can produce mineral scale, for example calcium carbonate, calcium sulfate, barium sulfate, calcium oxalate, calcium phosphate, silica, calcium silicate, magnesium silicate, fluorosilicate, aluminosilicate, strontium sulfate, calcium fluoride, magnesium hydroxide, and various iron or manganese compounds. The compositions and methods disclosed herein may be used to reduce or inhibit the formation of one or more types of scale. In exemplary embodiments, the scale-inhibiting polymer can be used as a scale inhibitor in any industrial water system where a scale inhibitor is needed. Suitable industrial water systems, include, without limitation, cooling tower water systems (including open recirculating, closed and once-through systems); petroleum wells, downhole formations, geothermal wells and other oil field applications; boilers and boiler water systems; mineral process waters including mineral washing, flotation and benefaction; paper mill digesters, washers, bleach plants and white water systems; black liquor evaporators in the pulp industry; gas scrubbers and air washers; continuous casting processes in the metallurgical industry; air conditioning and refrigeration systems; industrial and petroleum process water; indirect contact cooling and heating water, such as pasteurization water; water reclamation and purification systems; membrane filtration water systems; food processing streams (meat, vegetable, sugar beets, sugar cane, grain, poultry, fruit and soybean); and waste treatment systems as well as in clarifiers, liquid-solid applications, municipal sewage treatment and industrial or municipal water systems.
Scale-inhibiting polymers are often used in water treatment and oil field applications to minimize and/or prevent scale deposition. The deposition of scale can occur in the transport of aqueous mixtures and in subterranean rock formations due to the presence of water bearing alkaline earth metal cations such as calcium, barium, strontium, and the like as well as the presence of anions such as phosphate, sulfates, carbonates, silicates and the like. When these ions are in sufficient concentrations, a precipitate can form that builds up on interior surfaces of the conduits used for transport or in the subterranean rock formations, which restrict flow of the media of interest, e.g., water or oil. In oilfield applications, scales that are commonly formed include calcium sulfate, barium sulfate, and/or calcium carbonate that are generally formed in the fresh waters or brines used in well stimulation and the like as a result of increased concentrations of these particular ions, the water pH, pressures, and temperatures. In addition, calcium phosphate can form from the phosphate chemistry that is commonly used to treat wells and pipes for corrosion. The buildup of these mineral precipitates can reduce or block flow in the conduits and rock formations as well as cause other problems. In many cases, the first warning of the existence of a significant scale deposit may be a decline in well performance. In these instances, scale removal techniques may become necessary. As a result, a potentially substantial cost including downtime is required lost to effect repair as a result of scaling.
Scale-inhibiting materials are often added directly to a fluid to be treated or applied to oil bearing rock formations such as by means of “squeeze treatment”. A “squeeze” is an application of a treatment fluid or slurry into a treatment zone under pressure. In a squeeze application, the scale inhibitor may attach to the formation by chemical adsorption or by temperature-activated precipitation. When the well is put back into production, the scale inhibitor may leach out of the formation rock to treat the fluid. Some chemicals typically used in scale-inhibitor squeeze applications include phosphonated carboxylic acids or polymers.
The concentration of the scale inhibitor affects the effectiveness of the scale inhibitor. Each scale inhibitor has a predetermined “minimum inhibitor concentration” for a particular application. Above the minimum inhibitor concentration, scale formation may be effectively controlled. When the scale inhibitor concentration is below the minimum inhibitor concentration such as may occur during use, adsorption or degradation, additional amounts are then needed. For example, when a well is subjected to the squeeze application and then returned to operation, the concentration of the scale inhibitor in the produced fluids will diminish over time until such time that the scale inhibitor is at about or below the minimum inhibitor concentration. However, it can be difficult to determine when more scale inhibitor is needed and in which conduit or well it is needed. To address this problem, scale inhibitors may be tagged or labeled so that the presence or absence of the scale inhibitor can be readily detected. Scale inhibitor compounds have been tagged by introduction of specific atoms such as phosphorous or boron, which can be readily detected by inductively coupled plasma (ICP) analysis, thereby providing a means to detect the presence and/or concentration of the scale inhibitor.